1. Field of the Invention
This invention relates to a process for producing a toner used in image forming processes such as electrophotography, electrostatic recording and electrostatic printing, and to an apparatus for modifying surfaces of toner particles.
2. Related Background Art
In general, processes for producing toner particles may include a process making use of pulverization and a process making use of polymerization. Toner particles produced by the pulverization are, under existing circumstances, advantageous in that they can be produced at a lower cost than those produced by the polymerization, and are also at present widely used in toners used in copying machines and printers. In the case when toner particles are produced by the pulverization, a binder resin, a colorant and so forth are mixed in stated quantities, the mixture obtained is melt-kneaded, the kneaded product obtained is cooled, the kneaded product thus cooled to solidify is pulverized, the pulverized product obtained is classified to obtain toner particles having a stated particle size distribution, and a fluidity improver is externally added to the toner particles obtained, to produce a toner.
In recent years, copying machines and printers are demanded to achieve high image quality, energy saving, environmental adaptation and so forth. For these, toners are, in their technical concept, shifting over in the direction of making toner particles spherical in order to achieve high transfer efficiency and cut down waste toners. In order to achieve such technical concept by the pulverization, a method of making toner particles spherical by mechanical pulverization is proposed, as disclosed in Japanese Patent Application Laid-open No. H09-85741. Also, a method of making toner particles spherical by the action of hot air is proposed, as disclosed in Japanese Patent Application Laid-open No. 2000-29241. However, the method of making toner particles spherical by mechanical pulverization can not sufficiently achieve the aim at making spherical. Also, the method of making toner particles spherical by the action of hot air makes wax begin to melt when toner particles are incorporated with wax, to make it difficult to control surface properties of toner particles, leaving a problem on the quality stability of toner particles.
To cope with these, a surface modifying apparatus for modifying surfaces of toner particles is proposed which also enables high-performance surface treatment and removal of fine powder, as disclosed in Japanese Patent Application Laid-open No. 2002-233787. However, this surface modifying apparatus is desired to be improved, because it may be mentioned that, when a high degree of making spherical is maintained, fine-powder removal efficiency, what is called classification efficiency, tends to lower and also a phenomenon of image fog tends to occur.